There is a dramatic need for noninvasive real-time in vivo imaging of small animals at the University of Wisconsin-Madison. This need is centered around the study of host- microbe interactions. The equipment required to perform these investigations is the Xenogen IVIS Imaging System 200. The most significant benefit of this real-time in vivo imaging is far fewer mice will be used because the instrument allows a scientist to follow the same mouse throughout an experiment instead of using and sacrificing several mice at various time points. Light is emitted from within a living animal when D-Luciferin or Coelenterazine is injected and used as a substrate by firefly or renilla luciferases, respectively. Spectral imaging uses measurement data from a sequence of images filtered at different wavelengths ranging from 420 nm to 720 nm, to determine the depth and location of the bioluminescent reporter. The IVIS Imaging System 200 includes a sensitive CCD camera, a dark imaging chamber to minimize incident light, and a 22-filter wheel that permits both bioluminescent and fluorescent imaging. Turret-mounted custom lens provide 5 levels of magnification, from 26 cm to 2.9 cm, allowing high-resolution (60 [unreadable]m) detailed imaging. Living Image specialized software analyzes and quantifies the results, and can even perform 3D diffuse tomography reconstructions to visualize internal organs. All of these features - fluorescent and bioluminescent imaging with multiple reporters, high-resolution magnification, and 3D reconstruction - will give us great flexibility with our experiments. Sharing this particular instrument among this group of users is a beautiful example of exploiting the flexibility of a technology to its fullest. This instrument's imaging capabilities will enable users to visualize mouse/microbe interactions as well as the model symbiotic interactions between 1) the Hawaiian squid Euprymna scolopes and its luminous bacterial partner Vibrio fischeri, 2) the normal microbial flora of the gypsy moth midgut, and 3) the tripartite interaction between a nematode (Steinernema carpocapsae), larval stage insects, and a gamma-proteobacterium, Xenorhabdus nematophila. The University of Wisconsin-Madison is well known for leading the field of host-microbe interactions; it is our intent to develop these in vivo imaging models and reagents for our studies, and to make them available to other investigators across the country. [unreadable] [unreadable] [unreadable]